Testis & epididymis

Germ cell tumors

Carcinoid / well differentiated neuroendocrine tumor

Topic Completed: 1 September 2012

Minor changes: 28 December 2020

Copyright: 2002-2021, PathologyOutlines.com, Inc.

PubMed Search: carcinoid [title] well differentiated neuroendocrine tumor

Rafael Jimenez, M.D.
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Cite this page: Jimenez R. Carcinoid / well differentiated neuroendocrine tumor. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/testiscarcinoid.html. Accessed December 3rd, 2021.
Definition / general
  • Low grade neuroendocrine carcinoma, similar to counterpart at other sites
  • Usually monomorphic cells growing in solid nests, trabeculae or pseudoglands
  • Also called pure neuroendocrine carcinoma
  • Rare ( < 1% of testicular neoplasms), mean age 46 years
  • Carcinoid tumors are neuroendocrine tumors derived from enterochromaffin (Kulchitsky) cells that secrete serotonin and most commonly arise in GI and respiratory tracts
  • In testis, presumed to be a monodermal teratoma, although 20% have other teratomatous elements
Clinical features
  • Only 10% have clinical carcinoid syndrome
Prognostic factors
  • Metastatic disease is associated with carcinoid syndrome, tumor size 7 cm or more (Cancer 1993;72:1726)
Case reports
  • Excision; occasionally metastasizes
Gross description
  • Solid, yellowish tan, well circumscribed
  • Cysts reflect other teratomatous elements
Gross images

AFIP images

Solid, tan cut surface

Microscopic (histologic) description
  • Islands of cells forming small acini; cords forming rosettes or sheets
  • Cells have granular eosinophilic cytoplasm, round nuclei with granular chromatin
  • Usually no intratubular germ cell neoplasia, no / minimal mitotic activity, usually minimal atypia or necrosis
Microscopic (histologic) images

AFIP images

Well defined acini and
solid islands of cells
separated by fibrous stroma

Eosinophilic cytoplasm and
round nuclei with coarsely
granular chromatin

Images hosted on other servers:

Insular pattern, chromogranin+

Intratubular germ cell neoplasia

Placental-like alkaline phosphatase

Testicular carcinoid tumor

Cytology description
  • Isolated or sheets of tumor cells with granular cytoplasm, round nuclei, uniformly distributed fine chromatin
Negative stains
Electron microscopy description
  • Neurosecretory granules
Molecular / cytogenetics description
Differential diagnosis
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